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4106. X-ray lithography by synchrotron radiation of INS-ES. (USA)
Classified
abstracts
4099-4107
35 4099. Imaging and alignment tests on an electron projection system. (USA) Improvements to an Electron Projection System are described which eliminate many of the reported disadvantages to this type of system. The performance of a field-compensating electrostatic chuck that remedies pattern distortion caused by the wafer (anode) is described in conjunction with imaging and alignment tests on 75 mm dia wafers. Proximity effects and reimpacting backscattered electron flooding are shown to be minimized by reduction of the electron exposure energy thereby eliminating the need for pattern compensation in the mask. Line and space patterns with 0.5 Frn dimensions were exposed and resolved without compensation for exposure dosage of larger patterns. Overlay registration results are given for two-layer alignment tests using e-beam-fabricated masks to expose 75 mm dia wafers. W R Livesay, J Vuc Sci Technol, 15 (3), 1978, 1022-1027. 35 4100. Recent progress on the electron image projector. (USA) Three main aspects of the 1 : 1 electron image projector are considered; the economics, the ultimate resolution, and an electrostatic chuck. It is shown that the image projector is economic if more than four exposures per mask can be made; the resolution limitation due to the system is shown to be 200-300 A, but is in practice limited by electron scattering. The effect of electron scattering can be overcome by altering dimensions in patterns down to 1 pm, but isolated windows of 0.5 pm require ‘two-mode’ masks. The electrostatic chuck is shown to provide an adequate pressure to hold slices flat and adequate heat sinking. (GB) J P Scott, J Vuc Sci Technol, 15 (3), 1978, 1016-1021. 35 4101. Optical manipulation of resist profile in conformable printing. (USA) Differences between the developed photoresist profile and the optical image in the resist is a function of exposure and development conditions. Because of absorption of light in the photoresist and lateral etching by the developer, an overcut profile in the developed image of positive resists is inevitable, even if the distribution of the exposing light is perfectly verical. Intentional overexposure followed with quick development or the use of highly reflective substrates only minimizes the overcut. This paper describes an approach using a rotating plane wave making a predetermined angle with the optical axis to expose a mask-wafer assembly. This type of illumination produces an undercut optical image which compensates for the absorption and lateral etching effects. It also reduces the coherence in the illumination to give better images. The angle of inclination as well as the exposure-development parameters can be adjusted to manipulate the angle of cutting. Analytical intensity distribution based on geometric optics is given to provide an insight to the dependence of the cutting angle to the beam angle and the exposuredevelopment parameters. PMMA in the deep-uv wavelength region and AZl350J in the near-uv region are used to demonstrate the variation of the cutting angle and the liftoff process. B J Lin, J Vat Sci Technol, 15 (3), 1978, 1012-1015. 35 4102. Simulation of X-ray resist line edge profiles. (USA) X-ray resist line edge profiles are explored as a function of exposure mask and resist properties. The study is based on an exposurescission and development-etching model of positive resists. Development rate curves for two actual and three hypothetical resists are used. The simulation is implemented by using a string of points to follow the contour of the developer-resist interface as a function of development time. Control of the resist profile suitable for liftoff of 0.4 pm lines is explored in the context of low flux levels for a high throughput production environment. High aspect ratio lines (3: I) and profiles degradation due to mask edge effects for Al,, and CuL exposure are considered. A R Nereuther, J Vat Sci Technol, 15 (3), 1978, 1004-1008. 35 4103. Surface relief gratings of 3200 li period fabrication techniques and influence on thin-film growth. (USA) AS part of a project to study the effects of surface relief steps on thinfilm nucleation and growth, a technology for fabricating 1000 A linewidth surface relief gratings with control of sidewall profiles to a resolution of the order of 100 8, is under development. Laser holo328
graphic lithography and ion beam etching are used to produce gold gratings on 0.9 pm thick polyimide membrane masks. Next, these masks are replicated using CuL or CK X-ray lithography, thereby producing high aspect ratio relief gratings in PMMA having welldefined vertical sidewalls. Surface relief structures are then produced on substrates by liftoff, ion beam etching or reactive ion etching using the PMMA relief gratings. Such structures were decorated with gold nuclei using ion beam sputter deposition. The decoration experiments indicated a periodic variation in nuclei density and showed that the smoothness of the grating edges is of the order of 100 w. D C Flanders and H I Smith, J Vuc Sci Technol, 15 (3), 1978, 1001-1003. 35 4104. Fabrication of micro- and submicron-bubble memory devices by a mask transfer technique with subsequent getter-ion etching. (USA) In order to fabricate magnetic bubble memory circuits of high bit density using X-ray lithography, it is necessary to form accurate gold absorber patterns for X-ray masks and accurate permalloy patterns for the bubble memory circuits. The combined processes of mask transfer technique and getter-ion etching instead of conventional ion etching in pure argon gas were used to make patterns in these metal films. Pattern width accuracies within 10.1 pm and the angles of edge slope up to 70” were obtained by using these processes. Our new method was applied to the microfabrication of gold X-ray mask patterns and permalloy patterns of the circuits for magnetic bubbles diameters 0.95 and I .5 Wm. (Japan) T Funayama et al, J Vuc Sci Technol, 15 (3), 1978, 998-1000. 35 4105. Polyimide membrane X-ray lithography masks-fabrication and distortion measurements. (USA) A process for fabricating polyimide membrane X-ray lithography masks is described in detail. Thin membranes of polyimide are formed by spinning polyamic acid on Corning 021 I, or other glass substrates, and polymerizing in situ. The glass substrate acts as a holder and an efficient heat sink during formation of gold absorber patterns on top of the polyimide, a procedure that usually includes ion beam etching. A support ring is then bonded to the polyimide, and the glass etched in dilute hf. Optically smooth polyimide membranes with thicknesses from 0.5 to 5 pm are readily achieved. Measurements of the distortion of polyimide membrane X-ray lithography masks have been made using a holographic moirk method and a method based on measuring the spread in the angle of diffraction from gold-grating patterns. These indicated a distortion less than two parts in IO’ over the central 7.5 mm dia area of a 19 mm dia membrane. D C Flanders and H I Smith, J Vuc Sci Technol, 15 (3), 1978,995-997.
4106. X-ray lithography by synchrotron radiation of INS-ES. (US?) Synchrotron radiation from the electron-synchrotron INS-ES at the University of Tokyo has been used for X-ray lithography. Several mask patterns, such as the bubble pattern and the holographic grating pattern, are duplicated. Masks used are 0.4 pm thick gold on 3 pm silicon. At an electron energy of 1.l GeV the direct-total beam of synchrotron radiation can be used for mask replication. By using the grating-mask pattern with 692 nm period made by the halographic method, the grating pattern with a large height-to-width ratio is obtained. This result clearly demonstrates the high collimation of the X-ray beam from the synchrotron. (Japan) H Aritome et al, J Vat Sci Technol, 15 (3), 1978, 992-994. 35 4107. X-ray exposure system using finely position adjusting apparatus. (USA) An apparatus for finely adjusting the three dimensional position of a workpiece and the application of this apparatus to high power X-ray lithography are presented. The relative positioning apparatus has been designed, using electrodynamic transducers for the x, y and z directions and an electrostrictive transducer for rotary direction (0). Motions in each direction are supported by a resilient plate. The relative position of mask and wafer has been detected by applying a mechanical vibration to the wafer, with an accuracy of less than 10.1 pm. The fine positioning mechanisms have displayed excellent performance with high accuracies. As a first step to constructing a working apparatus, a prototype exposure system was built using pattern replication in an atmospheric environment, comprised of a
abstracts
4099-4107
35 4099. Imaging and alignment tests on an electron projection system. (USA) Improvements to an Electron Projection System are described which eliminate many of the reported disadvantages to this type of system. The performance of a field-compensating electrostatic chuck that remedies pattern distortion caused by the wafer (anode) is described in conjunction with imaging and alignment tests on 75 mm dia wafers. Proximity effects and reimpacting backscattered electron flooding are shown to be minimized by reduction of the electron exposure energy thereby eliminating the need for pattern compensation in the mask. Line and space patterns with 0.5 Frn dimensions were exposed and resolved without compensation for exposure dosage of larger patterns. Overlay registration results are given for two-layer alignment tests using e-beam-fabricated masks to expose 75 mm dia wafers. W R Livesay, J Vuc Sci Technol, 15 (3), 1978, 1022-1027. 35 4100. Recent progress on the electron image projector. (USA) Three main aspects of the 1 : 1 electron image projector are considered; the economics, the ultimate resolution, and an electrostatic chuck. It is shown that the image projector is economic if more than four exposures per mask can be made; the resolution limitation due to the system is shown to be 200-300 A, but is in practice limited by electron scattering. The effect of electron scattering can be overcome by altering dimensions in patterns down to 1 pm, but isolated windows of 0.5 pm require ‘two-mode’ masks. The electrostatic chuck is shown to provide an adequate pressure to hold slices flat and adequate heat sinking. (GB) J P Scott, J Vuc Sci Technol, 15 (3), 1978, 1016-1021. 35 4101. Optical manipulation of resist profile in conformable printing. (USA) Differences between the developed photoresist profile and the optical image in the resist is a function of exposure and development conditions. Because of absorption of light in the photoresist and lateral etching by the developer, an overcut profile in the developed image of positive resists is inevitable, even if the distribution of the exposing light is perfectly verical. Intentional overexposure followed with quick development or the use of highly reflective substrates only minimizes the overcut. This paper describes an approach using a rotating plane wave making a predetermined angle with the optical axis to expose a mask-wafer assembly. This type of illumination produces an undercut optical image which compensates for the absorption and lateral etching effects. It also reduces the coherence in the illumination to give better images. The angle of inclination as well as the exposure-development parameters can be adjusted to manipulate the angle of cutting. Analytical intensity distribution based on geometric optics is given to provide an insight to the dependence of the cutting angle to the beam angle and the exposuredevelopment parameters. PMMA in the deep-uv wavelength region and AZl350J in the near-uv region are used to demonstrate the variation of the cutting angle and the liftoff process. B J Lin, J Vat Sci Technol, 15 (3), 1978, 1012-1015. 35 4102. Simulation of X-ray resist line edge profiles. (USA) X-ray resist line edge profiles are explored as a function of exposure mask and resist properties. The study is based on an exposurescission and development-etching model of positive resists. Development rate curves for two actual and three hypothetical resists are used. The simulation is implemented by using a string of points to follow the contour of the developer-resist interface as a function of development time. Control of the resist profile suitable for liftoff of 0.4 pm lines is explored in the context of low flux levels for a high throughput production environment. High aspect ratio lines (3: I) and profiles degradation due to mask edge effects for Al,, and CuL exposure are considered. A R Nereuther, J Vat Sci Technol, 15 (3), 1978, 1004-1008. 35 4103. Surface relief gratings of 3200 li period fabrication techniques and influence on thin-film growth. (USA) AS part of a project to study the effects of surface relief steps on thinfilm nucleation and growth, a technology for fabricating 1000 A linewidth surface relief gratings with control of sidewall profiles to a resolution of the order of 100 8, is under development. Laser holo328
graphic lithography and ion beam etching are used to produce gold gratings on 0.9 pm thick polyimide membrane masks. Next, these masks are replicated using CuL or CK X-ray lithography, thereby producing high aspect ratio relief gratings in PMMA having welldefined vertical sidewalls. Surface relief structures are then produced on substrates by liftoff, ion beam etching or reactive ion etching using the PMMA relief gratings. Such structures were decorated with gold nuclei using ion beam sputter deposition. The decoration experiments indicated a periodic variation in nuclei density and showed that the smoothness of the grating edges is of the order of 100 w. D C Flanders and H I Smith, J Vuc Sci Technol, 15 (3), 1978, 1001-1003. 35 4104. Fabrication of micro- and submicron-bubble memory devices by a mask transfer technique with subsequent getter-ion etching. (USA) In order to fabricate magnetic bubble memory circuits of high bit density using X-ray lithography, it is necessary to form accurate gold absorber patterns for X-ray masks and accurate permalloy patterns for the bubble memory circuits. The combined processes of mask transfer technique and getter-ion etching instead of conventional ion etching in pure argon gas were used to make patterns in these metal films. Pattern width accuracies within 10.1 pm and the angles of edge slope up to 70” were obtained by using these processes. Our new method was applied to the microfabrication of gold X-ray mask patterns and permalloy patterns of the circuits for magnetic bubbles diameters 0.95 and I .5 Wm. (Japan) T Funayama et al, J Vuc Sci Technol, 15 (3), 1978, 998-1000. 35 4105. Polyimide membrane X-ray lithography masks-fabrication and distortion measurements. (USA) A process for fabricating polyimide membrane X-ray lithography masks is described in detail. Thin membranes of polyimide are formed by spinning polyamic acid on Corning 021 I, or other glass substrates, and polymerizing in situ. The glass substrate acts as a holder and an efficient heat sink during formation of gold absorber patterns on top of the polyimide, a procedure that usually includes ion beam etching. A support ring is then bonded to the polyimide, and the glass etched in dilute hf. Optically smooth polyimide membranes with thicknesses from 0.5 to 5 pm are readily achieved. Measurements of the distortion of polyimide membrane X-ray lithography masks have been made using a holographic moirk method and a method based on measuring the spread in the angle of diffraction from gold-grating patterns. These indicated a distortion less than two parts in IO’ over the central 7.5 mm dia area of a 19 mm dia membrane. D C Flanders and H I Smith, J Vuc Sci Technol, 15 (3), 1978,995-997.
4106. X-ray lithography by synchrotron radiation of INS-ES. (US?) Synchrotron radiation from the electron-synchrotron INS-ES at the University of Tokyo has been used for X-ray lithography. Several mask patterns, such as the bubble pattern and the holographic grating pattern, are duplicated. Masks used are 0.4 pm thick gold on 3 pm silicon. At an electron energy of 1.l GeV the direct-total beam of synchrotron radiation can be used for mask replication. By using the grating-mask pattern with 692 nm period made by the halographic method, the grating pattern with a large height-to-width ratio is obtained. This result clearly demonstrates the high collimation of the X-ray beam from the synchrotron. (Japan) H Aritome et al, J Vat Sci Technol, 15 (3), 1978, 992-994. 35 4107. X-ray exposure system using finely position adjusting apparatus. (USA) An apparatus for finely adjusting the three dimensional position of a workpiece and the application of this apparatus to high power X-ray lithography are presented. The relative positioning apparatus has been designed, using electrodynamic transducers for the x, y and z directions and an electrostrictive transducer for rotary direction (0). Motions in each direction are supported by a resilient plate. The relative position of mask and wafer has been detected by applying a mechanical vibration to the wafer, with an accuracy of less than 10.1 pm. The fine positioning mechanisms have displayed excellent performance with high accuracies. As a first step to constructing a working apparatus, a prototype exposure system was built using pattern replication in an atmospheric environment, comprised of a